The present invention relates to a vacuum switch with a vacuum exhaust element.
The interruption performance of a vacuum valve drops down suddenly at 10xe2x88x924 Torr or below. A change in vacuum pressure is caused not only by the leakage of vacuum due to generation of cracking but also by the release of gas molecules adsorbed in metal or insulating material, further by the transmission of atmospheric gas, and so on. When a vacuum vessel becomes larger in size as a higher rated voltage is requested of such a vacuum valve, the release of adsorbed gas or the transmission of atmospheric gas cannot be bypassed.
According to JP-A-51-130873, a vacuum exhaust element is attached so as to project from a vacuum vessel to the outside. However, the vacuum exhaust element is provided in portion connected to the bus. Therefore, there is a problem that an insulating transformer is required for a power source so that the whole size of the vacuum switch with the insulating transformer becomes larger.
It is an object of the present invention to provide a vacuum exhaust element of a vacuum switch which is miniaturized and which is safe for maintenance and inspection.
In order to attain the foregoing object, according to an aspect of the present invention, in a vacuum switch in which a pair of electrodes are disposed in opposition to each other in a grounded vacuum vessel so that one of the electrodes is detachably brought into contact with the other electrode, and rods connected with the electrodes extend to the outside from the grounded vacuum vessel, there is provided a vacuum exhaust element comprising: a projection portion projecting to the outside from a part of the grounded vacuum vessel; a magnetic field generator disposed outside the projection portion; and a power source circuit connected with an electrode and a getter which are provided in the projection portion.
According to another aspect of the present invention, a vacuum exhaust element has a projection portion projecting from a part of the grounded vacuum vessel in the same direction as one of rods connected to the electrodes respectively; a magnetic field generator disposed outside the projection portion; and a power source circuit connected with an electrode and a getter which are provided in the projection portion.
According to another aspect of the present invention, a vacuum exhaust element has a projection portion projecting from a part of the grounded vacuum vessel in the same direction as one of rods connected to the electrodes respectively; a magnetic field generator disposed outside the projection portion; and a power source circuit connected with an electrode and a getter which are provided in the projection portion. The vacuum exhaust element is made shorter than the one rod.
The vacuum exhaust element may be disposed under the one rod in opposition to each other.
In the vacuum exhaust element, the vacuum vessel and the power source circuit may be connected to the ground.
In the vacuum exhaust element, an insulator may be put between the grounded vacuum vessel and the projection portion.
In the vacuum exhaust element, the electrode provided in the projection portion may be constituted by a high-voltage-side electrode and a low-voltage-side electrode through an electric discharge gap.
In the vacuum exhaust element, a getter layer may be provided in an inner wall surface of the projection portion.
In the vacuum exhaust element, an insulation resistance meter may be connected to the power source circuit.